Evaluation of the Cytotoxic Profile of Metformin and Y15 in Platinum Resistant Ovarian Cancer Cells

Nova Southeastern University, Davie, Florida, USA

Objectives: This study evaluated the combined cytotoxic efficacy of metformin and the focal adhesion kinase (FAK) inhibitor Y15, in platinum resistant OVCAR3 ovarian cancer cells. Background: In previous studies, we demonstrated that metformin, an antidiabetic drug, induces cytotoxicity in platinum resistant ovarian cancer cells. Increased phosphorylation of FAK, a tyrosine kinase, is implicated in the development of this platinum resistance. We therefore evaluated the ability of metformin to enhance FAK inhibition in vitro. Methods: Cells were treated with Y15 (10-100 μM) and metformin (10-100Mm) separately, to determine IC10 values which were used for combination protocols (Y15 20μM + Metformin (10Mm). Following treatment, DNA fragmentation and poly ADP ribose polymerase (PARP) cleavage assays were used to evaluate mechanisms of cell death. Total and phosphorylated FAK, p53, p21, and BAX expression were also assessed using western blot. Results: Y15 significantly increased the efficacy of metformin compared to metformin only. Apoptotic cell death was confirmed by PARP cleavage and DNA fragmentation. Combination treatment with metformin and Y15 downregulated phosphorylated FAK expression, confirming reduced FAK activity. Reduced FAK phosphorylation correlated with increased expression of pro-apoptotic markers p53, p21 and BAX. Conclusions: Y15 enhances the cytotoxic profile of metformin in platinum resistant OVCAR 3 cells. This study is the first to report a FAK dependent cytotoxic mechanism of metformin in ovarian cancer. In further work, we will explore the mechanisms by which metformin increases Y15 mediated FAK inhibition. Grants: The authors thank the Royal Dames Inc. Ft. Lauderdale for financial support.